Most homeowners want one number before they sign anything: how long until the panels are on the roof and actually turning my meter backward. The honest answer has two parts, because the crew is only on your roof for a day or two, while the paperwork around it (design, permits, inspection, and utility approval) is what really sets the calendar. This guide walks the full solar installation timeline step by step, with real numbers from the U.S. Department of Energy, NREL, and EnergySage, an original phase-by-phase model you can plan against, and the delays that quietly add weeks.
The solar installation timeline at a glance (updated for 2026)
- Plan for about 2 to 6 months, contract to power-on. Installers often quote 60 to 90 days, and that is a fair best-to-typical case, but national project data put the median closer to 4.5 to 6 months, with only about 1 in 4 projects finishing inside 3 months (EnergySage, updated December 2024; NREL residential PV timelines, as of 2026).
- The panels themselves go up in 1 to 3 days. A typical 5 to 10 kW rooftop system is installed in about one day, sometimes two or three for a large or complex roof (U.S. Department of Energy, as of 2026).
- Permitting is the swing factor. Traditional local permits average about 7 to 9 business days and can stretch to several weeks, but DOE’s SolarAPP+ automated platform issues same-day, often instant approvals for qualifying systems (U.S. Department of Energy, SolarAPP+, as of 2026).
- Utility Permission to Operate (PTO) adds roughly 1 to 4 weeks. After inspection your utility signs off before you can switch on, with a median near 10 business days and a tail out to 6 to 8 weeks in busier territories (NREL interconnection analysis, as of 2026).
- A main panel upgrade is the most common hidden delay. If your electrical panel cannot host the solar breaker under the NEC 120% rule, an upgrade or an alternate connection method can add 1 to 3 weeks (NFPA 70, NEC 705.12, as of 2026).
How long does solar installation take from start to finish?
A typical residential solar project takes about 2 to 6 months from the day you sign to the day the utility grants Permission to Operate. Solar companies commonly quote 60 to 90 days, which is a reasonable best-to-typical estimate, but NREL’s analysis of real completed projects shows the national median runs closer to 4.5 to 6 months, and only about one in four projects finishes within three months (NREL, as of 2026; EnergySage, updated December 2024). The wide range is normal, because most of the calendar is spent waiting on your permit office and your utility, not on the crew.
Here is the part that surprises people: the physical work is the shortest step. The mounting, wiring, and inverter go in over 1 to 3 days (U.S. Department of Energy, as of 2026). Everything else on the timeline is design, review, and approval that happens before and after that short install window.
To make the range concrete, the table below is our own model of the elapsed time to each milestone under three market conditions. It is an estimate built from the phase ranges the sources above report, and it accounts for the fact that some steps overlap, so the total is shorter than adding every maximum.
Original model: elapsed time to each milestone (SolarFY estimate)
| Milestone (in order) | Typical duration of the step | Fast track, cumulative | Typical, cumulative | Slower market, cumulative |
|---|---|---|---|---|
| Contract signed | Day 0 | Week 0 | Week 0 | Week 0 |
| Site survey and assessment done | 1 to 3 weeks | End of week 1 | End of week 2 | End of week 3 |
| Design and permit paperwork ready | 1 to 3 weeks (overlaps survey) | End of week 2 | End of week 4 | End of week 6 |
| Building and electrical permit approved | Same day to 8 weeks | End of week 2 | End of week 7 | End of week 12 |
| Panels installed on the roof | 1 to 3 days | Week 4 | Week 9 | Week 15 |
| Local inspection passed | 1 to 3 weeks | Week 5 | Week 11 | Week 18 |
| Utility Permission to Operate, system on | 1 to 8 weeks | Week 6 | Week 13 | Week 22 |
| Contract to power-on | about 6 weeks | about 13 weeks (3 months) | about 22 weeks (5+ months) |
Assumptions: the crew is scheduled 1 to 3 weeks after the permit is issued; design and permit-document prep overlap the survey; the fast track assumes SolarAPP+ same-day permitting and a responsive utility; the slower market assumes manual permitting, a utility backlog, and one added step such as a panel upgrade or an HOA or historic review. Estimate only. Your project depends on your jurisdiction, your utility, and your installer. Sources for the underlying phase ranges: DOE, NREL, and EnergySage (as of 2026).
This model lines up with what the sources describe: a streamlined project can reach power-on in about six weeks, a typical one in about three months (the 60 to 90 days you will hear quoted), and a slower market can run five months or more, which is why the honest planning range is 2 to 6 months.
One number worth holding onto from the model: in the typical three-month case, your installer’s crew is on the roof for only about 1 to 2 days, under 2 percent of the whole calendar, while permitting, inspection, and utility approval account for the large majority of the wait. That is the single most useful reframe for planning: the delay you feel is almost never the installation itself.
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The solar installation timeline, step by step
Every residential project moves through the same seven stages, in this order. The durations below are the typical per-step ranges reported by DOE, NREL, and EnergySage (as of 2026). Knowing which step you are in tells you what is really holding things up.
1. Site survey and assessment (1 to 3 weeks after signing). Once you sign, the installer visits your home, or does a remote assessment, to measure the roof, check shading, and evaluate your electrical panel before finalizing the design (U.S. Department of Energy, as of 2026). Scheduling this visit is the main variable, and a busy installer backlog is the usual reason it lands at the far end of the range.
2. System design and engineering (1 to 3 weeks, often overlapping the survey). The installer finalizes the panel layout, inverter selection, and expected production, then prepares your permit documents (EnergySage, updated December 2024). Because the permit package is built here, this step usually runs alongside the survey rather than fully after it.
3. Permitting from your local authority (same day to 8 weeks). Your installer files for building and electrical permits with the local authority having jurisdiction (the AHJ). This is one of the two steps with the widest spread. A jurisdiction on DOE’s SolarAPP+ platform can return a same-day, automated approval, while a manual office can take several weeks (U.S. Department of Energy, SolarAPP+, as of 2026). Local rules vary a lot by region; our guide to solar permitting in Southern California breaks down the plan-check and Permission to Operate timelines across the Los Angeles, San Diego, and Inland Empire markets.
4. Installation on the roof (1 to 3 days). With permits in hand and materials available, the crew mounts the racking, sets the panels, and wires the inverter, usually finishing a typical home in a single day (U.S. Department of Energy, as of 2026). Scheduling the crew after permit issuance commonly adds 1 to 3 weeks before this day arrives.
5. Local inspection (1 to 3 weeks after installation). A local building or electrical inspector confirms the system meets code before it can connect (U.S. Department of Energy, as of 2026). Availability of the inspector, not the inspection itself, sets the wait.
6. Utility interconnection and Permission to Operate (1 to 8 weeks). Your installer submits interconnection paperwork, the utility reviews it, sometimes swaps your meter, and issues PTO, the green light to switch on and earn credits. The median is near 10 business days, with a tail to 6 to 8 weeks in busier territories (NREL, as of 2026).
7. Switch on. After PTO you turn the system on and net metering begins.
Note: The two steps you cannot rush are permitting and utility PTO, because both sit with outside offices. NREL’s project data attribute most of the variation in total timelines to the design, permitting, and installation-scheduling phases, so the fastest projects are the ones where the homeowner responds quickly and the installer knows the local AHJ and utility well.
How long does the actual installation take on install day?
For a typical home, the crew is on your roof for about one day. A standard 5 to 10 kW system is usually installed in a single working day, and a large or complex roof can run two to three days (EnergySage, updated December 2024; U.S. Department of Energy, as of 2026). This is the answer to the common searches for how long it takes to install 10 or 20 panels: the panel count changes the hours, not usually the number of days.
The estimate below converts the DOE and EnergySage guidance into crew-days by system size, for a typical two to four person crew. It is an estimate, since roof pitch, height, ground versus roof mounting, and adding a battery all change the hours.
Install-day crew time by system size (SolarFY estimate)
| System size | Roughly this many panels | On-site crew time |
|---|---|---|
| About 2 to 3 kW | 6 to 8 panels | A few hours, part of one day |
| About 4 kW | 10 panels | About 1 day |
| About 6 kW (typical home) | 14 to 16 panels | About 1 day |
| About 8 kW | 20 panels | 1 to 2 days |
| 10 kW or more, or a complex roof | 25+ panels | 2 to 3 days |
Estimate for a typical 2 to 4 person crew on a standard pitched asphalt-shingle roof, based on DOE and EnergySage install-day guidance (as of 2026). Adding a battery, a ground mount, a steep or tall roof, or electrical upgrades adds time. The panel count moves the hours; most homes still finish in 1 to 2 days.
Why permitting and utility approval drive the timeline
If your project is dragging, it is almost always sitting in a permit queue or a utility interconnection queue. These are the two outside offices on your critical path, and they are exactly where the automated tools and the slow manual processes diverge the most.
DOE’s SolarAPP+ is the single biggest permitting accelerator. SolarAPP+ is an automated permitting platform built by NREL and funded by DOE that runs an instant code-compliance check for qualifying residential rooftop systems. In participating jurisdictions it turns a permit that used to take days or weeks into a same-day, often instant approval (U.S. Department of Energy, as of 2026; U.S. Department of Energy, SolarAPP+ success story, December 2022).
Permitting: automated versus manual
| Factor | Traditional manual permitting | DOE SolarAPP+ (participating jurisdictions) |
|---|---|---|
| Who reviews | A person at the local permit office | An automated code-compliance check |
| Typical time to approval | About 7 to 9 business days, up to several weeks in busy offices | Same day, often minutes for a compliant application |
| Application effort | Varies by office | The application takes roughly 15 minutes |
| Non-standard systems | Manual review | Routed to manual review, not instant |
Source: U.S. Department of Energy and NREL SolarAPP+ program materials and evaluations (as of 2026). Complex or non-standard systems are sent to normal manual review rather than instant approval.
Utility Permission to Operate is the other queue. After inspection, your utility must review the interconnection and issue PTO before you can switch on. This runs about 1 to 4 weeks for most homes, with a median near 10 business days, though a busy utility can push it to 6 to 8 weeks or more (NREL, as of 2026). You cannot speed up the utility, but choosing an installer who files clean interconnection paperwork the first time avoids the back-and-forth that adds weeks. For a closer look at how these two approvals work, see our guide to solar permits and interconnection.
What can add weeks to your solar installation
The published timeline assumes a clean, standard project. The items below are the common reasons a real project runs long. Any one of them can move you from the typical column into the slower one.
Common delay drivers and how much time they add
| Delay driver | What it is | Time it can add |
|---|---|---|
| Main panel upgrade (NEC 120% rule) | Your existing electrical panel cannot host the solar breaker under NEC 705.12, so it needs an upgrade or an alternate connection | 1 to 3 weeks, plus a utility disconnect and reconnect |
| HOA or architectural review | A homeowners association must approve the design and placement | 2 to 6 weeks |
| Historic-district or landmark review | A local historic commission must sign off on visible exterior work | 4 to 8 weeks |
| Roof repair or replacement first | The roof must be sound before panels go on | Several weeks to months |
| Utility interconnection backlog | The utility is processing a high volume of applications | Several extra weeks |
| Manual permitting (no SolarAPP+) | Your jurisdiction reviews permits by hand | Days to several weeks versus same-day |
Time ranges are typical estimates synthesized from DOE, NREL, and industry guidance (as of 2026). Your jurisdiction and utility set the actual figures.
The panel upgrade deserves a plain-English note, because it is the most common surprise. The NEC 120% rule (NEC 705.12) limits how much solar you can back-feed through your existing electrical panel. If your panel cannot accommodate the solar breaker, the fix is often a main panel upgrade, which adds an electrician visit and usually a utility disconnect and reconnect (NFPA 70, NEC 705.12, as of 2026). Worth knowing: a panel upgrade is not the only legal fix. Depending on your setup, an installer can use a supply-side (line-side) connection, derate the backfeed breaker, or add a power control system, which can avoid a full upgrade. A good site survey flags this early, so ask about it before you sign.
How your state, utility, and installer change the timeline
Where you live is the biggest reason two homeowners see very different timelines. States that have adopted streamlined or automated permitting tend to sit at the fast end, while an area with manual permitting and a congested utility sits at the slow end. The clearest example is California, where a 2022 law (SB 379) requires cities and counties above a population threshold to offer an automated, instant online permitting platform for residential solar and names DOE’s SolarAPP+ as a qualifying option (California Legislature, SB 379, as of 2026). Adoption is spreading nationally, with DOE reporting 160 communities across 10 states automating solar permitting through SolarAPP+ as of December 2023 (U.S. Department of Energy, December 2023). This is why homeowner-reported timelines vary so much from one place to the next.
Your installer’s backlog and local experience also matter. A large national provider and a smaller local company can have very different scheduling backlogs at any given moment, and an installer who works your specific AHJ and utility every week clears the paperwork faster than one who does not. This is about scheduling and local know-how, not about any one company being “better,” so compare on concrete criteria rather than a ranking. Reasonable questions to ask any installer: what is your realistic contract-to-PTO timeline for my town, do you file through SolarAPP+ where it is available, and who handles the interconnection paperwork. For a fuller checklist, see the right questions to ask a solar installer.
One timeline pressure that is now gone: the federal tax-credit deadline. For years, buyers rushed to place a system in service by December 31 to claim the 30% federal Residential Clean Energy Credit. That credit (Section 25D) ended for systems placed in service after December 31, 2025, so there is no longer a year-end federal deadline forcing your schedule (IRS, as of 2026). State and utility programs and net metering may still apply, so the smarter reason to start early now is your own bill, not a federal cutoff. For what changed, see what the federal solar tax credit change means in 2026.
How to keep your solar installation on schedule
You control more of the timeline than you might think. A few habits keep a project in the fast lane:
- Respond same-day to document and signature requests, since design and paperwork are on your critical path.
- Ask whether your jurisdiction uses SolarAPP+ or another instant-permitting path, and favor an installer who files through it.
- Get your roof and electrical panel checked in the survey, so a roof repair or a panel upgrade is known before it becomes a mid-project surprise.
- Pick an installer who works your utility and AHJ regularly, so interconnection paperwork is right the first time.
- Ask for a written, town-specific timeline in your quote, not a generic one.
If you are still deciding whether solar makes sense for your home before you worry about scheduling, start with solar basics for homeowners and how net metering credits your production. To turn a timeline into dollars, our solar cost and savings guide and whether solar panels are worth it run the payback math. You can also see how MySolarFY matches you with installers and the data and methodology behind these guides.
Frequently asked questions
How long does it take to install solar panels from start to finish?
Plan for about 2 to 6 months from signing the contract to the utility granting Permission to Operate. Solar companies often quote 60 to 90 days, which is a fair best-to-typical estimate, but NREL’s data on real completed projects show a national median closer to 4.5 to 6 months, with only about 1 in 4 finishing within 3 months (NREL, as of 2026; EnergySage, updated December 2024). Most of that time is design, permitting, inspection, and utility approval, not the physical install, which takes only 1 to 3 days.
How long does the physical solar panel installation take on install day?
The crew is usually on your roof for about one day. A typical 5 to 10 kW system is installed in a single working day, and a large or complex roof can take two to three days (U.S. Department of Energy, as of 2026). The number of panels changes the hours more than the number of days, so a 10-panel and a 20-panel job both commonly finish in one to two days. This is only the mounting and wiring, and it does not include the inspection and utility approval that follow.
Why does solar permitting and utility approval take so long?
They are handled by outside offices on your critical path, so they set the calendar more than the crew does. Traditional local permits average about 7 to 9 business days and can stretch to weeks, though DOE’s SolarAPP+ platform issues same-day, often instant approvals for qualifying systems (U.S. Department of Energy, as of 2026). After installation, utility Permission to Operate adds roughly 1 to 4 weeks, with a tail to 6 to 8 weeks in busy territories (NREL, as of 2026). An installer who knows your AHJ and utility clears both faster.
What is the 120% rule and can it delay my solar installation?
The 120% rule comes from the National Electrical Code (NEC 705.12) and limits how much solar you can back-feed through your existing electrical panel. If your panel cannot host the solar breaker, one common fix is a main panel upgrade, which can add 1 to 3 weeks plus a utility disconnect and reconnect (NFPA 70, as of 2026). A panel upgrade is not the only option, though. An installer can sometimes use a supply-side connection, derate the backfeed breaker, or add a power control system instead. A thorough site survey flags this early, so ask about your panel before you sign.
How long does it take to break even after installing solar panels?
Break-even is a different clock from the installation timeline. Installation is measured in weeks to a few months, while payback, the point where your savings equal what you paid, is measured in years and depends on your electric rate, system cost, financing, and local incentives. The install timeline does not change your payback period. To estimate yours, use our solar cost and savings guide and the analysis of whether solar panels are worth it, which walk through the payback math for your situation.
Does the federal solar tax credit still affect when I should install?
No, that deadline is gone. Homeowners used to rush to place a system in service by December 31 to claim the 30% federal Residential Clean Energy Credit, but Section 25D ended for systems placed in service after December 31, 2025, so there is no longer a year-end federal deadline driving your schedule (IRS, as of 2026). A separate commercial credit, Section 48E, can apply to leased or PPA systems, but the company that owns the system claims it, not the homeowner. MySolarFY does not provide tax advice; confirm your situation with a tax professional.
Reviewed by the SolarFY Editor in July 2026. Figures were verified against the linked U.S. Department of Energy, NREL, EnergySage, NFPA, IRS, and California Legislature sources as of July 2026. Permitting, interconnection, and Permission to Operate timelines change by jurisdiction and utility and can shift over time, so confirm current local timelines with your installer, your permit office, and your utility before you plan around a date. MySolarFY does not provide tax, legal, or financial advice; consult a licensed professional about your own situation. Learn more about how MySolarFY works and our data and methodology.
MySolarFY is a free service that matches homeowners with licensed solar installers. We are not an installer, financing company, or government program. “No up-front cost” refers to qualifying lease or PPA financing, where eligible homeowners may have no out-of-pocket cost at installation. Lease and PPA terms typically run 20 to 25 years, may include an annual price escalator, and total payments may exceed the cost of a cash purchase; on a lease or PPA the tax benefits and any incentives go to the company that owns the system, not the homeowner. Homeowners do not get the federal residential credit that ended after December 31, 2025. This is not free solar, and monthly payments apply. Eligibility, savings, incentives, and timelines vary and are not guaranteed. See our full disclaimer.
